Blends of amorphous polyamides and polyarylates, poly(ester carbonates) or polycarbonates are known to exhibit desirable properties including excellent solvent resistance, ductility and resistance to brittle failure when molded into articles. See, for example, the copending, commonly assigned U.S. patent application of L. M. Maresca, D. C. Claggett and U. S. Wascher, Ser. No. 812,433 filed Dec. 23, 1985. Novel polyamide-polyarylate copolymers have been prepared which have excellent and improved physical and mechanical properties, and good chemical resistance and barrier properties, and these are the subject matter of commonly assigned copending application Ser. No. 117,250, filed Nov. 4, 1987. Such copolymers are prepared in a one or two stage melt polymerization process in which a wide variety of diamines, diphenols and diacid esters can be used. If, for example, diphenyl iso/terephthalate is reacted with a diamine in the melt at, for example, 120.degree. C.-270.degree. C., amide units are produced. If a diphenol such as bisphenol-A is included and a temperature of 220.degree. C.-320.degree. C. is employed arlyate units will also be smoothly produced. Although Fox and Shafer, U.S. Pat. No. 4,567,249, disclose the melt preparation of polyamides by amine-ester interchange, there is no hint or suggestion in that patent to employ both a diamine and a diphenol in the process to obtain polyamide-polyarylate copolymers.
It has now been found that amide-urea copolymers, including random copolymers, block copolymers and alternating copolymers, can be synthesized by a melt polymerization process. If carried out stepwise, in one step a polyamide block can be formed by the reaction of a diamine, e.g., hexamethylenediamine or meta-xylylenediamine, with a diaryl ester, e.g., diphenyl iso/terephthalate, at temperatures ranging from about 120.degree. to about 270.degree. C. In a separate step, additional diamine and diaryl ester of carbonic acid are added to the reaction to form the polyurea-block at similar temperatures, i.e., more moderate than required to make the polyarylate blocks. Random polyamide-ureas can be conveniently formed in a one step melt polymerization process by reacting a diamine with a diaryl ester such as diphenyl isophthalate and a diaryl ester such as diphenyl carbonate at 120.degree.-270.degree. C. The new materials, which can be made from a wide variety of diamines, have excellent mechanical and physical properties, good chemical resistance and barrier properties.